This paper presents a contactless power transfer system for automatic-guided vehicles (AGVs). The system can replace batteries and, therefore, can improve the operation ratio and load capacity of an AGV. The contactless power transformer in this system was designed to enhance the mutual inductance between the primary and secondary. The secondary involving a diode rectifier was modeled to an equivalent circuit, which takes voltage drops across the diodes into account. Based on the model, an optimal primary current control technique maximizing the transfer efficiency was derived. Contactless power transfer tests to the AGV using a prototype of the contactless power transformer were conducted. It is confirmed that the power transfer over 100 W with transfer efficiencies of 80% can be achieved. Furthermore, it is confirmed that the proposed control technique can improve the system efficiency during AGV drive operation.